Development of biomimetic ceramic-based materials is currently a challenge in dental tissue engineering. Synthetic hybrid chitosan (CS)-hydroxyapatite (HAP) layers are regarded as candidates for ...teeth remineralization, protection against further demineralization ensuring also antibacterial activity. Thus, the aim of this work was to obtain new biomimetic CS-HAP layers for restoration of damaged mature enamels and to pursue morphological, compositional, structural and hardness modifications of the grown layers by immersion for 4, 7 and 10 days into artificial saliva (AS) under CS-Emdogain (EMD) hydrogel action. SEM-EDX, HRTEM-SAED, FTIR and micro-Raman findings indicated formation of carbonate-substituted HAP, B-type, with c-axis orientation in the newly formed CS-HAP coatings. Prolonged immersion span of 10 days caused increasing CS content in the superficial grown layer while carbonate content diminished. Optimum Ca/P ratio (1.85at%) and hardness of 2.48GPa were recorded for seven days growth using CS-EMD hydrogel. Subtle changes in HAP lattice parameters were recorded for 10-day grown layer while c-axis orientation of HAP crystals at mesoscale was preserved. Mechanism of CS interaction during in situ biomimetic synthesis and self-assembly of HAP crystals under CS-EMD hydrogel presence is also discussed.
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Developing multifunctional systems for the biomimetic remineralization of human enamel is a challenging task, since hydroxyapatite (HAP) rod structures of tooth enamel are difficult to replicate ...artificially. The paper presents the first report on the simultaneous use of chitosan (CS) and agarose (A) in a biopolymer-based hydrogel for the biomimetic remineralization of an acid-etched native enamel surface during 4–10-day immersion in artificial saliva with or without (control group) fluoride. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, Fourier transform infrared and Raman spectroscopies, X-ray diffraction, and microhardness tests were applied to investigate the properties of the acid-etched and remineralized dental enamel layers under A and CS-A hydrogels. The results show that all biomimetic epitaxial reconstructed layers consist mostly of a similar hierarchical HAP structure to the native enamel from nano- to microscale. An analogous Ca/P ratio (1.64) to natural tooth enamel and microhardness recovery of 77.4% of the enamel-like layer are obtained by a 7-day remineralization process in artificial saliva under CS-A hydrogels. The CS component reduced carbonation and moderated the formation of HAP nanorods in addition to providing an extracellular matrix to support growing enamel-like structures. Such activity lacked in samples exposed to A-hydrogel only. These data suggest the potential of the CS-A hydrogel in guiding the formation of hard tissues as dental enamel.
ZnO is one of the most studied oxides due to its nontoxic nature and remarkable properties. It has antibacterial and UV-protection properties, high thermal conductivity, and high refractive index. ...Various ways have been used to synthesize and fabricate coinage metals doped ZnO, but the sol-gel technique has received a lot of interest because of its safety, low cost, and facile deposition equipment. Coinage metals are represented by the three nonradioactive elements of group 11 of the periodic table: gold, silver, and copper. This paper, which was motivated by the lack of reviews on the topic, provides a summary of the synthesis of Cu, Ag, and Au-doped ZnO nanostructures with an emphasis on the sol-gel process and identifies the numerous factors that affect the morphological, structural, optical, electrical, and magnetic properties of the produced materials. This is accomplished by tabulating and discussing a summary of a number of parameters and applications that were published in the existing literature over the previous five years (2017-2022). The main applications being pursued involve biomaterials, photocatalysts, energy storage materials, and microelectronics. This review ought to serve as a helpful reference point for researchers looking into the many physicochemical characteristics of coinage metals doped ZnO, as well as how these characteristics vary according to the conditions under which experiments are conducted.
One of the current research objectives is the development of new films for the conservation of glass heritage objects. The value of historical glass objects is given by the technology and raw ...materials used in production as well as their transparency and color. Their colors are correlated with oxide composition rich in transitional metals, which decrease resistance of corrosive agents from the atmosphere. In this paper, SiO
-ZnO gels have been designed to protect historical glass objects. The sol-gel method used to obtain gels is a powerful tool for functionalizing different materials. An important functionalization is the antibacterial activity. By applying a gel, the coated material is able to decrease the growth of bacteria. After deposition, some gels must be strengthened by heat treatment. The effect of ZnO content (10 mol% and 20 mol%) on the properties of the studied gels was investigated by Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and antibacterial tests.
ATCC 25922,
ATCC 25923, and the halotolerant bacterium,
, isolated from a salt crystal from Unirea mine, Slănic Prahova, Romania, were used. The gel Gel 2 (SiO
-ZnO (20 mol%)) showed the best properties.
Intelligent textiles are obtained by “in situ” polymerization of aniline on viscose and polyamide as flexible substrates. Intelligent textiles are materials with electrical, mechanical, and thermal ...properties that improve the quality of life. The wide range of electrical or optical properties, and good environmental stability of emeraldine base and salt form make polyaniline (PANI) attractive for a variety of applications. The PANI is doped with p‐toluene sulfonic acid by direct route. The structure of the coated textiles is characterized by infrared spectroscopy with attenuated total reflectance device. The morphologies of the obtained textiles are investigated by scanning electron microscopy. Viscose and polyamide textiles are coated uniform and show good electrical properties. After coating with doped PANI, electrical properties of textile materials increase by 108 times. The best results are obtained for viscose.
The objective of our investigations consists in the thermal characterization of SiO
2
-PbO-Na
2
O vitreous materials in order to establish their properties for applications mainly as sealants. In ...order to evaluate the vitreous material − metal adherence, the thermal expansion coefficients (α) from experimental and theoretic data were determined. The differential thermal analysis of studied materials give the information about temperatures characteristic to glass transition, crystallization and melting. Dilatometer measurements were performed in air atmosphere in order to establish thermal coefficients of the materials. Softening and flowing characteristic of the vitreous materials were established by heating microscope measurements. The difference between thermal expansion coefficient (α) of the vitreous materials (10.2 × 10
−6
K
−1
and 17.6 × 10
−6
K
−1
) and thermal expansion coefficient of the steel substrate OL 38 (10.8 × 10
−6
K
−1
) is under 37%. This value is fit for a good adherence between materials.
In this paper, we conducted a fundamental study concerning the effect of thermal treatment on the structure and morphology of 2 mol% vanadium doped ZnO nanopowders obtained by microwave assisted ...sol-gel method (MW). The samples were analyzed by DTA, FTIR, XRD, SEM, and UV-Vis spectroscopy. The DTA results showed that above 500 °C, there was no mass loss in the TG curves, and ZnO crystallization occurred. The XRD patterns of the thermally treated powders at 500 °C and 650 °C showed the crystallization of ZnO (zincite) belonging to the wurtzite-type structure. It was found that in the 650 °C thermally treated powder, aside from ZnO, traces of Zn
(VO
)
existed. FTIR spectra of the annealed samples confirmed the formation of the ZnO crystalline phase and V-O bands. The micrographs revealed that the temperature influenced the morphology. The increase in the annealing temperature led to the grain growth. The SEM images of the MW powder thermally treated at 650 °C showed two types of grains: hexagonal grains and cylindrical nanorods. UV-Vis spectra showed that the absorption band also increased with the increasing temperature of thermal treatment. The MW sample annealed at 650 °C had the highest absorption in ultraviolet domain.
In the last years the interest for protection of the historical objects has increased. Among them a high number of ancient and middle age objects were made from lead silicate glasses. Such historical ...objects from glass contain small quantities (below 5wt%) of transitional elements as Cu, Ag, Fe, which decrease their resistance at weathering. Previous investigations show that protective sol–gel silica coating does not change the appearance of artistic alkali silicate glasses when it is deposited on their surface. In the present paper model lead silicate glasses with compositions similar to ancient objects were studied. Their chemical resistance in water, morphology and structure was investigated, being established that the iron added into glass changed the corrosion mechanism. In order to prevent the weathering of the synthesized glasses, a protective thin film was applied on surface. All glasses show a better resistance at water attack after coating with a film of silica gel.
Acid rain is a major problem for animals, plants, buildings, and also for the top glass of photovoltaic (PV) solar panels and greenhouses. Air pollutants such as NOx, NH3, and H2S can mix with water ...in the atmosphere to form acid rain. It was discovered that atmospheric water vapor adsorbed on the surface of glass can also lead to corrosion of the glass surface. The purpose of this work is to obtain a protective film for glasses used in different domains such as solar cells, windows, stained glass windows from historical buildings, etc. Thin film deposited on glass must be protective against acid rain, transparent in the visible domain with a band gap up to 3.2 eV, and have a vitreous structure (glass). Electron beam (e-gun) technology is a deposition technique for producing high-purity and dense coatings in a short time. It is well known that Ta2O5 is an oxide with anticorrosive properties, but it is expensive and cannot form glass by itself. ZnO is an oxide known as a glass former, exhibiting good optical properties. In this paper, a thin film obtained by the deposition of ZnO and Ta2O5 on a glass substrate using e-gun technology are studied. The simulated acid rain effect on the structure, morphology, and optical properties of thin films are studied after a 65% nitric acid attack on the surface. The X-ray diffraction (XRD) pattern shows the vitreous state of the thin film with a composition 50%ZnO 50%Ta2O5 before and after the acid attack. The morphology, composition, and thickness of the film are investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and profilometry.
In the present work, we report a systematic study of the phase formation and sintering ability of different oxide compositions in the SnO2–ZnO binary system using solid state reactions. For some ...selected compositions mechanically activated powders were also investigated. Structural and morphological characterizations of the samples were performed by X-ray diffraction (XRD), FT-IR Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Only the formation of Zn2SnO4 binary compound was revealed in the experimental conditions. Based on the structural results the subsolidus equilibrium phase diagram was established. The sintering ability of the studied samples was also determined, establishing the compositions domains of obtaining dense or porous ceramics. The investigation by impedance spectroscopy in the 300–600K temperature range shows that all studied samples exhibit n-type semiconductor behavior with low values of the activation energy (0.18–0.34eV).
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